The pleural cavity and the pleura serve an important function of aiding in the optimal functioning of the lungs during respiration. The pleural cavity consists of the visceral pleural layer which covers the lungs, the parietal pleural layer that lines the chest wall, and the thin layer of fluid that separates the two. Diseases affecting the pleural cavity and pleura include pleural effusions and pneumothorax. Pleural effusions involve the build-up of excess fluid around the lungs, and pleural effusions result from accumulation of fluid in the pleural space. Pleural effusions can be associated with conditions such as cancer, tuberculosis, congestive heart failure, pneumonia, pulmonary emboli, viral disease, cirrhosis, post-coronary artery bypass graft surgery, gastrointestinal disease, tuberculosis pancreatitis, and mesothelioma. Pneumothorax occurs when air or gas is present in the pleural cavity.
Patients with pleural diseases such as symptomatic pleural effusions or pneumothorax are typically treated with thoracentesis to remove fluid or air, and/or chemical or mechanical pleurodesis.
Removal of excessive fluids from the pleural space is an important part of treating symptomatic pleural effusions. An excess of fluids in the pleural space can result in chest pain, shortness of breath upon mild exertion and/or at rest, and general discomfort in a patient. In addition to relieving these symptoms, the removal of excessive pleural fluid is important, as the fluid occasionally becomes infected and can cause further complications in a patient.
Pleurodesis is also a common treatment for patients with recurrent symptomatic pleural effusions. Pleurodesis involves chemical or mechanical irritation of the parietal and/or visceral layers of the pleura in order to close off the pleural space and prevent further fluid and/or air accumulations. Pleurodesis is typically characterized by the creation of fibrous adhesions between the parietal and visceral layers of the pleura. Chemical pleurodesis can be achieved with the insertion of sclerosing agents, typically by catheter, into the pleural space. Sclerosing agents include talc, tetracycline, doxycycline, minocycline, doxorubicin, povidone iodine, bleomycin, TGFβ and silver nitrate.
The pleural fluid of patients with symptomatic pleural effusions is often aspirated or removed for diagnostic testing. For example, a diagnostic pleural fluid sample may be aspirated from the pleural space with a needle and syringe and analyzed for the presence of proteins, enzymes, and microbes. In addition, the cytology and the pH of the fluid may be tested. Maskell et al. “BTS Guidelines for the Investigation of a Unilateral Pleural Effusion in Adults,” Thorax, 2003, 58: ii8-ii17.
Removal of fluid from the pleural space should be monitored carefully to reduce the possibility of adverse effects, such as re-expansion pulmonary edema. Typically, fluid removal should not exceed about 1.5 L per sitting. However, based on the individual patient, greater amounts of pleural fluid may be removed. Feller-Kopman D., “Large-volume Thoracentesis and the Risk of Re-expansion Pulmonary Edema,” Ann Thorac Surg, 2007; 84(5): 1656-1661.
Some patients, including patients with recurrent malignant pleural effusions, require periodic removal of pleural fluid, to relieve symptoms and decrease the risk of medical complications. The removal of pleural fluid can be done at the hospital on an in-patient basis, or on an outpatient basis. After the removal of excessive pleural fluid, patients often experience an increase in total lung capacity and an improvement in their symptoms. Antony et al. “Management of Malignant Pleural Effusions,” Eur Respir J. 2001; 18: 402-419.
Typically, the frequency at which patients receive treatments of pleural fluid removal is based on their symptoms. For example, outpatients often receive an initial treatment of pleural fluid removal, and they receive subsequent treatments based on when their symptoms return. Patients typically receive treatments every 2 to 7 days. Alternatively, patients receiving inpatient pleurodesis typically require only one treatment. However, there are problems with either approach. Patients receiving outpatient fluid removal treatments can achieve “spontaneous” pleurodesis, but in a relatively long timeframe and at unsatisfactory success rates. Patients receiving inpatient pleurodesis undergo a procedure that is often painful, requires a 4-7 day hospital stay, and has a relatively high recurrence rate. One theory that attempts to explain this is that the rapid re-accumulation of fluid in the pleural space makes it more difficult for the parietal and visceral layers of the pleura to adhere and close off the pleural space.
There is a need in the art for a method of quickly and successfully treating pleural effusion in subjects, allowing patients to obtain relief from symptoms quickly and safely.
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